Pipes which are used in dwellings, and commercial buildings or in industrial plants and which carry steam for steam heat, hot water, cold water, chemicals, or petroleum products and the like are generally provided with an exterior layer of insulation. Such pipes may be formed of copper, steel, aluminum, plastic, rubber, or other like materials. This exterior layer of insulation frequently comprises jackets or sleeves which are wrapped around the pipe. These jackets or sleeves are generally applied in segments which abut one another. Each segment comprises a generally cylindrically shaped block of insulation having a centrally disposed, anally aligned channel adapted to receive the pipe. The material forming the insulation sleeve may be a flexible elastomeric material. Each segment is slit along its axial length so that the pipe may pass through the split and reside within the central channel. The type of insulation material that has proven to be the best in conjunction with air conditioning or refrigeration units is a vinyl nitrile foam which is extruded into a tubular shape with the internal diameter being about the external diameter of the pipe to be insulated, such vinyl nitrile foam being quite flexible, and easily contourable to various radii and/or paths of the pipe to be insulated. Other foam insulation materials are also known. Normally the vinyl nitrile or other type of foam insulation tubing will come in lengths of approximately 6-8 feet with internal diameters ranging from 1 to 8 inches and external diameters of 2 to 10 inches, whereby the thickness of the wall is about 1/2 to 2 inches. The 6-8 foot lengths are convenient to be handled by a workman installing this insulation material after a refrigeration or air conditioning unit has been put into place. Typically, the vinyl nitrile tubular foam has a single slit longitudinally of the length so that the slit can be pulled back manually by the installer to slip the tubular insulation over the pipe. After an insulation sleeve has been placed around a pipe, the portions of the pipe on opposite sides of the slit are brought together and sealed. Sealing has been accomplished generally by applying an adhesive, typically a pressure-sensitive adhesive, to one or both of the opposed faces of the slit, which are brought together in sealing engagement, or alternatively, by providing on the outer surface of the insulation sleeve on one side of the slit a longitudinally extending flap which comprise a pressure-sensitive adhesive on a backing, the pressure-sensitive adhesive is pressed into engagement with the outer surface of the insulation sleeve on the opposite side of the slit.
Adhesive joints of the type described above have frequently proved to be short lived. This is due in part to the stresses within the insulation jacket or sleeve, which tend to pull the portions of the sleeve on opposite sides of the slit apart and to create a great deal of stress on the adhesive joint. Also while there have been many systems for closing the slit in such foam pipe insulations, including putting pressure-sensitive adhesive on to opposite sides of the slit, and then bringing those adhesives together, there has always been a significant problem in getting good pressure-sensitive adhesive anchorage, especially to a vinyl nitrile foam insulation material, as well as other types of foam insulation materials, and still achieving a good pressure-sensitive adhesive bonding relationship between the outwardly exposed adhesive to the adhesive on the opposite side of the slit.
Shrinkage in elastomeric foam insulation sleeves has been reported to be in the order of 2%. Shrinkage has been recognized as a problem which leads to stress along the longitudinal slit. Stresses are also formed during the extrusion process. Still other sources of stress occur during storage and shipment of finished sleeves. Insulation sleeves as extruded are cylindrical with a circular cross section. In storage, due to the weight of a sleeve itself and to sleeves stacked above it, the shape becomes distorted so that it takes on an oval or elliptical form. Also, sleeves are frequently compressed into an elliptical shape to reduce the sleeve's internal void space. As a consequence, it is necessary to use a sleeve whose nominal inside diameter (which assumes that the sleeve is still circular in shape) is slightly to somewhat larger than the outside diameter of the pipe to be encased. As a result upon installation, stress is placed on the sleeve on either side of the slit tending to pull apart an adhesive joint. This tendency to pull the adhesive joint apart is observed, whether adhesive is applied to the opposite faces of the slit or by means of a longitudinally extending pressure-sensitive tape applied to the outside surface on either side of the slit
As used herein, the term "pressure-sensitive adhesive" means the adhesive is tacky at ambient temperature whereas a "hot melt adhesive" is dependent upon temperature elevation, wherein the adhesive becomes tacky only upon temperature elevation. While the preferred embodiment of this invention appears more applicable to a pressure-sensitive adhesive, it could also be applicable to a hot melt adhesive.